Scroll compressor with a bypass

ABSTRACT

An upper back pressure type scroll compressor having a bypass is provided. The scroll compressor may include a casing, a discharge cover, a main frame, a first scroll supported by the main frame, and a second scroll that forms a suction chamber, an intermediate pressure chamber, and a discharge chamber together with the first scroll. The second scroll may include a bypass hole that communicates with the intermediate pressure chamber. The scroll compressor may also include a back pressure chamber assembly coupled to an upper portion of the second scroll by a fastening device and a bypass valve to open and close the bypass hole. The back pressure chamber assembly may include a discharge path by which the discharge chamber and the discharge space may communicate with each other and a bypass valve to open and close the bypass hole.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to Korean Application Nos. 10-2013-0028775, filed in Korea on Mar. 18, 2013, 10-2013-0028783 filed in Korea on Mar. 18, 2013, and 10-2013-0028791, filed in Korea on Mar. 18, 2013, as well as U.S. application Ser. Nos. ______ (Attorney Docket No. P-1232) filed in the U.S. on ______, and ______ (Attorney Docket No. P-1236), filed in the U.S. on ______, the contents of all of which are incorporated by reference herein in their entirety.

BACKGROUND

1. Field

A compressor, and more particularly, a scroll compressor with a bypass are disclosed herein.

2. Background

Scroll compressors are known. However, they suffer from various disadvantages.

A scroll compressor refers to a compressor that utilizes a first or orbital scroll having a spiral wrap and a second or fixed scroll having a spiral wrap, the first scroll performing an orbital motion with respect to the second scroll. While the first scroll and the second scroll are engaged with each other in operation, a capacity of a pressure chamber formed therebetween may be reduced as the first scroll performs the orbital motion. Hence, the pressure of a fluid in the pressure chamber may be increased, and the fluid discharged from a discharge opening formed at a central portion of the second scroll.

The scroll compressor performs a suction process, a compression process, and a discharge process consecutively while the first scroll performs the orbital motion. Because of operational characteristics, the scroll compressor may not require a discharge valve and a suction valve in principle, and its structure may be simple with a small number of components, thus making it possible to perform a high speed rotation. Further, as the change in torque required for compression is small and the suction and compression processes consecutively performed, the scroll compressor is known to create minimal noise and vibration.

For the scroll compressor, an occurrence of leakage of a refrigerant between the first scroll and the second scroll should be avoided or kept at a minimum, and lubricity (lubrication characteristic) should be enhanced therebetween. In order to prevent a compressed refrigerant from leaking between the first scroll and the second scroll, an end of a wrap portion should be adhered to a surface of a plate portion. On the other hand, in order for the first scroll to smoothly perform an orbital motion with respect to the second scroll, resistance due to friction should be minimized. The relationship between the prevention of the refrigerant leakage and the enhancement of the lubricity is contradictory. That is, if the end of the wrap portion and the surface of the plate portion are adhered to each other with an excessive force, leakage may be prevented. However, in such a case, more friction between the parts may result, thereby increasing noise and abrasion. On the other hand, if the end of the wrap portion and the surface of the plate portion are adhered to each other with less than an adequate sealing force, the friction may be reduced, but the lowering of the sealing force may result in the increase of leakage.

In order to solve such problems, a back pressure chamber having an intermediate pressure between a discharge pressure and a suction pressure may be formed on a rear surface of the first scroll or the second scroll. That is, the first scroll and the second scroll may be adhered to each other with proper force, by forming a back pressure chamber that communicates with a compression chamber having an intermediate pressure, among a plurality of compression chambers formed between the first scroll and the second scroll. With such a configuration, leakage of refrigerant may be prevented and lubricity enhanced.

The back pressure chamber may be positioned on a lower surface of the first scroll or an upper surface of the second scroll. In this case, the scroll compressor with such a back pressure chamber may be referred to as a ‘lower back pressure type scroll compressor’ or an ‘upper back pressure type scroll compressor’ for convenience. The structure of the lower back pressure type scroll compressor is simple, and its bypass holes easily formed. However, as its back pressure chamber is positioned on the lower surface of the first scroll, the form and position of the back pressure chamber may change due to the orbital motion. This may cause the first scroll to tilt, resulting in the occurrence of vibration and noise. Further, an O-ring to prevent leakage of a compressed refrigerant may be rapidly abraded. The structure of the upper back pressure type scroll compressor is complicated. However, as the back pressure chamber of the upper back pressure type scroll compressor is fixed in form and position, the probability of the second scroll tilting is low, and sealing for the back pressure chamber is excellent.

Korean Patent Application No. 10-2000-0037517 entitled Method For Processing Bearing Housing and Scroll Machine having Bearing Housing, which corresponds to U.S. Pat. No. 5,156,539 and U.S. Reissue Pat. No. 35,216, all of which are hereby incorporated by reference, discloses an example of such an upper back pressure type scroll compressor. FIG. 1 is a partial cross-sectional view of an upper back pressure type scroll compressor. The scroll compressor 1 of FIG. 1 may include a first or orbital scroll 30 configured to perform an orbital motion on a main frame 20 fixedly-installed in a casing 10 and a second or fixed scroll 40 engaged with the first scroll 30 to create a plurality of compression chambers upon the orbital motion. A back pressure chamber BP may be formed at an upper portion of the second scroll 40, and a floating plate 60 to seal the back pressure chamber BP may be installed so as to be slidable up and down along an outer circumferential surface of a discharge passage 45. A discharge cover 2 may be installed at an upper surface of the floating plate 60, thereby dividing an inner space of the scroll compressor 1 into a suction space (S) and a discharge space (D). A lip seal (not shown) may be installed between the floating plate 60 and the back pressure chamber BP, so that refrigerant may be prevented from leaking from the back pressure chamber BP.

The back pressure chamber BP may communicate with one of the plurality of compression chambers, and may be at a receiving end of an intermediate pressure from the plurality of compression chambers. With such a configuration, pressure may be applied upward to the floating plate 60, and pressure may also be applied downward to the second scroll 40. If the floating plate 60 moves upward due to pressure of the back pressure chamber BP, the discharge space D may be sealed as an end of the floating plate 60 contacts the discharge cover 2. In this case, the second scroll 40 moves downward to be adhered to the first scroll 30. With such a configuration, a gap between the second scroll 40 and the first scroll 30 may be effectively sealed.

Korean Patent Application No. 10-2012-7023733, which corresponds to U.S. Patent Pub. No. 2011/0206548, both of which are hereby incorporated by reference, discloses a compressor having a valve assembly. FIG. 2 is a sectional view of a fixed or second scroll of an upper back pressure type scroll compressor. The compressor of FIG. 2 may include a hub member 76 positioned at a central portion of the back pressure chamber BP and formed to pass through the back pressure chamber BP in upper and lower directions, and a valve assembly 28 disposed below the hub member 76. With such a configuration, bypass holes 90 and 92 formed on an upper surface of the second scroll 40 may be open and closed while the valve assembly 28 moves the hub member 76 up and down. For example, the bypass holes 90 and 92 may be open when the intermediate pressure is higher than the discharge pressure, thus pushing the valve assembly 28 up. Accordingly, overload in the upper back pressure type scroll compressor may be prevented by alleviating the pressure imbalance using the bypass holes.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein:

FIG. 1 is a cross-sectional view of an upper back pressure type scroll compressor;

FIG. 2 is a cross-sectional view of a second scroll of an upper back pressure type scroll compressor;

FIG. 3 is a cross-sectional view of an upper back pressure type scroll compressor having a back pressure discharge according an embodiment;

FIG. 4 is a partial cut-out perspective view showing a coupled state between a second scroll and a back pressure chamber assembly of FIG. 3;

FIG. 5 is an exploded perspective view of the second scroll and the back pressure chamber assembly of FIG. 3;

FIG. 6 is a perspective view of the second scroll of FIG. 3;

FIG. 7 is a planar view of a lower surface of a back pressure plate of FIG. 3;

FIG. 8 is an enlarged cross-sectional view of a portion of the second scroll and the back pressure plate of FIG. 3;

FIG. 9 is a partial cut-out cross-sectional view for explaining operation of a check valve and a discharge valve of FIG. 3;

FIG. 10 is a partial cut-out view of the scroll compressor of FIG. 3 with a retainer according to an embodiment;

FIG. 11 is a perspective view of a bypass valve according to another embodiment;

FIG. 12 is a cross-sectional view of a bypass valve according to another embodiment; and

FIG. 13 is a perspective view of a bypass valve according to yet another embodiment.

DETAILED DESCRIPTION

Description will now be given in detail of embodiments, with reference to the accompanying drawings. Where possible, like reference numerals have been utilized to indicate like elements, and repetitive disclosure has been omitted.

Referring again to FIG. 2, overload in the upper back pressure type scroll compressor may be prevented by alleviating pressure imbalance using the bypass holes and associated components of the scroll compressor. However, as the hub member 76 may be disposed in the back pressure chamber BP, the position of the bypass holes 90, 92 may not be set arbitrarily. That is, in order to obtain a sufficient back pressure with the back pressure chamber BP, the back pressure chamber BP should be formed at a predetermined position with a predetermined size. This may limit a size of the hub member 76. Therefore, positions of the bypass holes 90, 92 may be restricted to a region below the hub member 76.

Further, the floating plate 60 should seal the back pressure chamber BP while contacting an inner surface of the back pressure chamber BP of the second scroll 40 and an outer circumferential surface of the hub member 76. In this case, a sealing performance of the floating plate 60 may be compromised due to a quality of surface processing performed on the outer circumferential surface of the hub member 76, that is a processing allowance (tolerance) and a coupling allowance (tolerance) of the hub member 76.

Therefore, embodiments disclosed herein further provide a scroll compressor capable of forming bypass holes at arbitrary positions of the second scroll. Embodiments disclosed herein further provide a scroll compressor capable of using a bypass valve of a simple structure.

FIG. 3 is a cross-sectional view of an upper back pressure type scroll having a bypass according to an embodiment. FIG. 4 is a partial cut-out perspective view showing a coupled state between a second scroll and a back pressure chamber assembly of FIG. 3. FIG. 5 is an exploded perspective view of the second scroll and the back pressure chamber assembly of FIG. 3.

Referring to FIG. 3, a scroll compressor 100 having a bypass according to an embodiment may include a casing 110 having a suction space (S) and a discharge space (D), which are discussed hereinbelow. An inner space of the casing 110 may be divided into the suction space (S) and the discharge space (D) by a discharge cover 102 installed above at an upper portion of the casing 110. A space above the discharge cover 102 may correspond to the discharge space (D), and a space below the discharge cover 102 may correspond to the suction space (S). A suction port (not shown) that communicates with the suction space (S) and a discharge port (not shown) that communicates with the discharge space (D) may be fixed to the casing 110, respectively, thereby sucking a refrigerant into the casing 110 or discharging a refrigerant outside of the casing 110, respectively.

A stator 112 and a rotor 114 may be provided below the suction space (S). The stator 112 may be fixed to an inner wall surface of the casing 110, for example, in a shrinkage fitting manner. A rotational shaft 116 may be inserted into a central portion of the rotor 114, and may be rotated by power supplied from the outside.

A lower side of the rotational shaft 116 may be rotatably supported by an auxiliary bearing 117 installed below at a lower portion of the casing 110. The auxiliary bearing 117 may be supported by a lower frame 118 fixed to an inner surface of the casing 110, thereby stably supporting the rotational shaft 116. The lower frame 118 may be fixed to an inner wall surface of the casing 110, for example, by welding, and a bottom lower surface of the casing 110 may be used as an oil storage space. Oil stored in the oil storage space may be upward transferred upward by the rotational shaft 116, so that the oil may be uniformly supplied into the casing 110.

An upper end of the rotational shaft 116 may be rotatably supported by a main frame 120. The main frame 120 may be fixed to an inner wall surface of the casing 110, similar to the lower frame 118. A main bearing portion 122 may protrude downward from a lower surface of the main frame 120, and the rotational shaft 116 may be inserted into the main bearing portion 122. An inner wall surface of the main bearing portion 122 may serve as a bearing surface and support the rotational shaft 116 together with the aforementioned oil, so that the rotational shaft 116 may rotate in a smooth manner.

A first or orbital scroll 130 may be disposed on an upper surface of the main frame 120. The first scroll 130 may include a plate portion 132, which may have an approximate disc shape, and a wrap 134 spirally formed on one side surface of the plate portion 132. The wrap 134 may form a plurality of compression chambers together with a wrap 144 of a fixed or second scroll 140, which is discussed hereinbelow. The plate portion 132 of the first scroll 130 may perform an orbital motion while supported by an upper surface of the main frame 120. An Oldham ring 136 may be installed between the plate portion 132 and the main frame 120, thereby preventing rotation of the first scroll 130. A boss portion 138, into which the rotational shaft 116 may be inserted, may be formed on a lower surface of the plate portion 132 of the first scroll 130, thus allowing the first scroll 130 to perform an orbital motion by a rotational force of the rotational shaft 116.

The second scroll 140, which engages the orbital scroll 130, may be disposed above the first scroll 130. The second scroll 140 may be installed to be movable up and down with respect to the first scroll 130. More specifically, the second scroll 140 may be disposed on an upper surface of the main frame 120 using, for example, a fastener, for example, three guide pins 104, fitted into the main frame 120 inserted into three (3) guide holes 141 formed on an outer circumference of the second scroll 140.

The guide holes 141 may be formed at three pin supporting portions 142 that protrude from an outer circumferential surface of a body portion of the second scroll 140. The number of the guide pins 104 or pin supporting portions 142 may be arbitrarily set, and thus, the number is not limited to three.

The second scroll 140 may include a plate portion 143, which may have a disc shape. The wrap 144, which engages the wrap 134 of the first scroll 130, may be formed below the plate portion 143. The wrap 144 may have a spiral shape, and a discharge opening 145, through which a compressed refrigerant may be discharged, may be formed at a central portion of the plate portion 143. A suction opening 146, through which a refrigerant disposed in the suction space (S) may be sucked, may be formed on a side surface of the second scroll 140, so that the refrigerant may be sucked to the suction opening 146 by an interaction between the wrap 144 and the wrap 134.

As discussed above, the wrap 144 and the wrap 134 form a plurality of compression chambers. As the plurality of compression chambers decrease in volume while orbiting toward the discharge opening 145, a refrigerant is compressed. As a result, a pressure of a compression chamber adjacent to the suction opening 146 may be minimized, and a pressure of a compression chamber that communicates with the discharge opening 145 may be maximized. A pressure of a compression chamber positioned between the two above-mentioned compression chambers may have an intermediate pressure halfway between a suction pressure adjacent the suction opening 146 and a discharge pressure adjacent the discharge opening 145. The intermediate pressure may be applied to a back pressure chamber (BP), which is discussed hereinbelow, and may press the second scroll 140 toward the first scroll 130. Therefore, an intermediate pressure discharge opening 147, which may communicate with one of the intermediate pressure chambers, and through which a refrigerant may be discharged, may be formed at the plate portion 143, referring to FIG. 5.

An intermediate pressure sealing groove 147 a, into which an intermediate pressure O-ring 147 b that prevents leakage of a discharged refrigerant having the intermediate pressure may be inserted, may be formed near the intermediate pressure discharge opening 147. The intermediate pressure sealing groove 147 a may be formed in an approximately circular shape to enclose the intermediate pressure discharge opening 147. However, the shape is not limited to the circular shape. Further, the intermediate pressure sealing groove 147 a may be formed at other than the plate portion 143 of the fixed scroll 140. For instance, the intermediate pressure sealing groove 147 a may be formed on a lower surface of a back pressure plate 150, which is discussed hereinbelow.

Bolt coupling holes 148 for coupling bolts 106, which couple the back pressure plate 150 and the second scroll 140, may be formed on the plate portion 143 of the second scroll 140. In this embodiment, the number of the bolt coupling holes 148 is four, but embodiments are not so limited.

Referring to FIG. 6, bypass holes 149 may be formed at both sides of the discharge opening 145. The bypass holes 149 may pass through the plate portion 143, and extend up to the plurality of compression chambers formed by the wrap 144 and the wrap 134. The position of the bypass holes 149 may be differently set according to an operating condition. The bypass holes 149 may be formed to communicate with the compression chambers having a pressure 1.5 times higher than the suction pressure. The bypass holes 149 may include two through-holes, and a wall portion 149 a that encloses an outer circumferential portion of the two through-holes may be provided. The wall portion 149 a may contact a valve body of a bypass valve, which is discussed hereinbelow, and the wall portion 149 a may provide a space in which a refrigerant discharged from the through-holes may stay temporarily.

A valve seat portion 149 b may be formed near the bypass hole 149. The valve seat portion 149 b may provide a space through or in which a valve supporting portion of a bypass valve, which is discussed hereinbelow, may move, and may extend from an outer circumferential portion of the wall portion 149 a in one direction.

Referring to FIG. 5, the bypass valve 124 may include a valve supporting portion 124 a fixed to the plate portion 143 of the second scroll 140 by, for exmaple, rivets. The valve supporting portion 124 a may have a circular arc shape, and may be fixed to the plate portion 143 by, for example, two rivets. Alternatively, a coupling device such as bolts or screws, rather than the rivets, may be used. The valve supporting portion 124 a may extend from portions to which the rivets are coupled in a ‘V’ shape. For convenience, the extending portions may be referred to as connection portions 124 b. Valve bodies 124 c may be formed at ends of the connection portions 124 b. The valve body 124 c may maintain contact with the wall portion 149 a when no external force is applied thereto, and may have a diameter large enough to completely cover the wall portion 149 a.

A back pressure chamber assembly may be installed on the plate portion 143 of the second scroll 140. The back pressure chamber assembly may include a back pressure plate 150 and a floating plate 160, and may be fixed to an upper portion of the plate portion 143 of the second scroll 143. The back pressure plate 150 may have a ring shape, and may include a supporting plate 152 that contacts the plate portion 143 of the second scroll 140. The supporting plate 152 may have a ring shape, and may be formed to allow an intermediate pressure suction opening 153 that communicates with the aforementioned intermediate pressure discharge opening 147 to pass therethrough, referring to FIG. 7. Further, bolt coupling holes 154 that communicate with the bolt coupling holes 148 of the plate portion 143 of the second scroll 140 may be formed at or in the supporting plate 152.

An O-ring 155 a may be disposed between a lower surface of the supporting plate 152 and an upper surface of the second scroll 140. The O-ring 155 a, which may prevent a refrigerant from leaking from a gap between the supporting plate 152 and the second scroll 140, may be fitted into a ring-shaped groove 155 formed on an upper surface of the second scroll 140. Further, the O-ring 155 a may be forcibly pressed while the second scroll 140 and the back pressure plate 150 are coupled to each other by the bolts 106, thereby sealing a gap between the second scroll 140 and the back pressure plate 150. Alternatively, the ring-shaped groove 155 may be formed on a lower surface of the supporting plate 152, rather than on the second scroll 140.

The back pressure plate 150 may include a first ring-shaped wall 158 and a second ring-shaped wall 159 formed to enclose an inner circumferential surface and an outer circumferential surface of the supporting plate 152, respectively. The first ring-shaped wall 158 and the second ring-shaped wall 159 may form a space having a specific shape together with the supporting plate 152. The space may implement the aforementioned back pressure chamber (BP). The first ring-shaped wall 158 may extend upward from a central portion of the supporting plate 152, and include an upper surface 158 a may cover an upper end of the first ring-shaped wall 158. The first ring-shaped wall 158 may have a cylindrical shape with an open end.

An inner space of the first ring-shaped wall 158 may communicate with the discharge opening 145, thereby implementing a portion of a discharge path along which a discharged refrigerant may be transferred to the discharge space (D). As shown in FIGS. 4 and 9, a discharge check valve 108, which may have a cylindrical shape, may be disposed above the discharge opening 145. More specifically, a lower end of the discharge check valve 108 may be large enough to completely cover the discharge opening 145. With such a configuration, in a case in which the discharge check valve 108 contacts the plate portion 143 of the second scroll 140, the discharge check valve 108 may block the discharge opening 145.

The discharge check valve 108 may be installed in a valve guide portion 158 b formed at an inner space of the first ring-shaped wall 158, and the valve guide portion 158 b may guide an up-and-down motion of the discharge check valve 108. The valve guide portion 158 b may pass through the inner space of the first ring-shaped wall 158. An inner diameter of the valve guide portion 158 b may be the same as an outer diameter of the discharge check valve 108, to guide an up-and-down motion of the discharge check valve 108 above the discharge opening 145. However, the inner diameter of the valve guide portion 158 b may not be completely equal to the outer diameter of the discharge check valve 108 to facilitate movement of the discharge check valve 108.

A discharge pressure applying hole 158 c that communicates with the valve guide portion 158 b may be formed at a central portion of an upper surface of the first ring-shaped wall 158. The discharge pressure applying hole 158 c may communicate with the discharge space (D). Accordingly, in a case in which a refrigerant from the discharge space (D) backflows to the discharge opening 145, pressure applied to the discharge pressure applying hole 158 c may become higher than the pressure of the discharge opening 145. As a result, the discharge check valve 108 may move downward to block the discharge opening 145. If the pressure at the discharge opening 145 increases to be higher than the pressure at the discharge space (D), the discharge check valve 108 may move upward to open the discharge opening 145.

One or more intermediate discharge opening(s) 158 d may be formed outside of the valve guide portion 158 b. The one of more intermediate discharge opening(s) 158 d may provide a path through which a refrigerant discharged from the discharge opening 145 may move to the discharge space (D). In this embodiment, four (4) intermediate discharge openings 158 d are radially disposed; however, the number of the intermediate discharge openings 158 d may vary. The one or more intermediate discharge opening(s) 158 d may pierce through the first ring-shaped wall 158 extending from its bottom to its top. The one or more intermediate discharge opening(s) 158 d and the valve guide portion 158 b may communicate with each other at a lower end of the back pressure plate 150. That is, a stepped portion 158 e may be formed in a connection portion between the first ring-shaped wall 158 and the supporting plate 152. A discharged refrigerant reaches a space defined by the stepped portion 158 e, and then moves to the one or more intermediate discharge opening(s) 158 d.

A groove portion 161 to form a bypass path may be formed outside the stepped portion 158 e in a radial direction. The groove portion 161 may have a circular arc shape to enclose a portion of an outer circumferential portion of the stepped portion 158 e, and may be concaved from a lower surface of the supporting plate 152. Along an outer circumferential portion of the groove portion 161 extending in a radial direction, regions adjacent to the bolt coupling holes 154 may protrude inward in a radial direction. This may allow a peripheral portion of the bolt coupling holes 154 to maintain a sufficient strength.

An inner circumferential portion of the groove portion 161 in the radial direction may be open towards the stepped portion 158 e. With such a configuration, an inner space of the groove portion 161 may communicate with the one or more intermediate discharge opening(s) 158 d via the stepped portion 158 e.

A portion 161 a of an upper surface of the groove portion 161 (bottom surface in FIG. 7) may restrict an upward motion of the valve body 124 c, which may be referred to as an open degree restrictor 161 a for convenience. The open degree restrictor 161 a may be in a shape corresponding to the valve body 124 c, and may protrude toward the stepped portion 158 e. The open degree restrictor 161 a may be positioned above the valve body 124 c. Accordingly, in a case in which the valve body 124 c moves upward by a distance more than a predetermined value, the valve body 124 c may contact the open degree restrictor 161 a to prevent the valve body 124 c from moving any further.

Instead of the open degree restrictor, an additional retainer may be provided. As shown in FIG. 10, a retainer 161 b to restrict an open degree of the valve body 124 c when the valve body 124 c is open may be formed on an upper surface of the groove portion 161.

In some cases, the stepped portion 158 e may not be provided, but rather, a communication hole to communicate the valve guide portion 158 b and the one or more intermediate discharge opening(s) 158 d with each other may be provided. In any case, a refrigerant having passed through the discharge opening 145 may not be discharged to the one or more intermediate discharge opening(s) 158 d if the discharge check valve 108 is closed. The stepped portion 158 e may be formed in the plate portion 143 of the second scroll 140, rather than on the back pressure plate 150.

The groove portion may be formed on an upper surface of the plate portion 143 of the second scroll 140, rather than on a lower surface of the supporting plate. In such a case, the bypass hole and the bypass valve may be formed on a bottom surface of the groove portion. With such a configuration, a length of the bypass hole may be shortened, and thus a dead volume formed by the bypass hole may be reduced.

The second ring-shaped wall 159 may be spaced from the first ring-shaped wall 158 by a predetermined distance, and a first sealing insertion groove 159 a may be formed on an inner circumferential surface of the second ring-shaped wall 159. The first sealing insertion groove 159 a may serve to receive and fix an O-ring 159 b, to prevent leakage of a refrigerant from a contact surface to a floating plate 160, which is discussed hereinbelow. Alternatively, the first sealing insertion groove 159 a may be formed on an outer circumferential surface of the floating plate 160. However, the first sealing insertion groove 159 a formed on the floating plate 160 may be less stable than the first sealing insertion groove 159 a formed on the back pressure plate 150, because the floating plate 160 continuously moves up and down.

A space having an approximately ‘U’-shaped section may be formed by the first ring-shaped wall 158, the second ring-shaped wall 159, and the supporting plate 152. The floating plate 160 may be installed to cover the space. The floating plate 160 may have a ring shape, and be configured such to have an inner circumferential surface thereof face an outer circumferential surface of the first ring-shaped wall 158, and to have an outer circumferential surface thereof face an inner circumferential surface of the second ring-shaped wall 159. With such a configuration, the back pressure chamber (BP) may be implemented, and the aforementioned O-rings 159 b and 162 a interposed between the respective facing surfaces may serve to prevent a refrigerant inside the back pressure chamber (BP) from leaking to the outside. Further, bolt accommodation portions 106 a, which may prevent interference with the bolts 106, may be formed on a lower surface of the floating plate 160. However, in a case in which heads of the bolts 106 do not protrude from a surface of the supporting plate 152, the bolt accommodation portion 106 a may be omitted.

A second sealing insertion groove 162 to receive and fix the O-ring 162 a may be formed on the inner circumferential surface of the floating plate 160. The second sealing insertion groove 162 may be provided at or in the inner circumferential surface of the floating plate 160, whereas the first sealing insertion groove 159 a may be formed or in at the second ring-shaped wall 159. This is because the first ring-shaped wall 158 may have an insufficient margin to process the grooves due to the valve guide portion 158 b and the one or more intermediate discharge opening(s) 158 d formed therein, and a diameter of the first ring-shaped wall 158 may be smaller than a diameter the second ring-shaped wall 159. Alternatively, if the first ring-shaped wall 158 has a large diameter and a sufficient margin to process the grooves, the second sealing insertion groove 162 may be formed in the first ring-shaped wall 158.

A sealing end 164 may be provided at an upper end of the floating plate 160. The sealing end 164 may protrude upward from the surface of the floating plate 160, and may have an inner diameter large enough not to cover the one or more intermediate discharge opening(s) 158 d. The sealing end 164 may contact a lower side surface of the discharge cover 102, thereby sealing the discharge path so that a discharged refrigerant may be discharged to the discharge space (D) without leaking to the suction space (S).

Hereinafter, an operation of a compressor according to an embodiment will be explained.

When power is supplied to the stator 112, the rotational shaft 116 may rotate. As the rotational shaft 116 rotates, the first scroll 130 fixed to the upper end of the rotational shaft 116 may perform an orbital motion with respect to the second scroll 140. As a result, the plurality of compression chambers formed between the wrap 144 and the wrap 134 may move toward the discharge opening 145, thereby compressing a refrigerant.

If the plurality of compression chambers communicate with the intermediate pressure discharge opening 147 before the refrigerant reaches the discharge opening 145, a portion of the refrigerant may be introduced into the intermediate pressure suction opening 153 of the supporting plate 152. Accordingly, an intermediate pressure may be applied to the back pressure chamber (BP) formed by the back pressure plate 150 and the floating plate 160. As a result, pressure may be applied downward to the back pressure plate 150, whereas pressure may be applied upward to the floating plate 160.

Since the back pressure plate 150 may be coupled to the second scroll 140 by, for example, bolts, an intermediate pressure of the back pressure chamber (BP) may also influence the second scroll 140. The floating plate 160 may move upward because the second scroll 140 cannot move downward due to contact with the plate portion 132 of the first scroll 130. As the sealing end 164 contacts the lower end of the discharge cover 102, the floating plate 160 stops moving. Then, as the second scroll 140 is pushed toward the first scroll 130 by the pressure of the back pressure chamber (BP), the refrigerant may be prevented from leaking from a gap between the first scroll 130 and the second scroll 140.

If a pressure of the discharge opening 145 becomes higher than a pressure of the discharge space (D), the discharge check valve 108 may move upward so that the refrigerant may be discharged to the space defined by the stepped portion 158 e. Then, the refrigerant may be introduced into the one or more intermediate discharge opening(s) 158 d, and may then be discharged to the discharge space (D). If the scroll compressor 100 is stopped or a pressure of the discharge space (D) temporarily increases, the discharge check valve 108 may move downward to block the discharge opening 145. This may prevent counter rotation of the second scroll 140 resulting from backflow of the refrigerant.

As the groove portion 161 communicates with the discharge path via the stepped portion 158 e, a discharge pressure may be applied to the groove portion 161. Pressure of the intermediate pressure chamber may be applied to a lower surface of the valve body 124 c. In a normal operating condition, the valve body 124 c may maintain a contact state to the wall portion 149 a and the bypass hole 149 may be closed, because the discharge pressure is greater than the intermediate pressure.

However, if the suction pressure increases due to a change in operating condition, the intermediate pressure, which is normally about 1.5 times higher than the suction pressure, may become higher than the discharge pressure. In a case of the scroll compressor, the discharge pressure has a value obtained by multiplying the suction pressure with a compression ratio, while the compression ratio is fixed. Accordingly, if the suction pressure exceeds a proper range, the discharge pressure may excessively increases causing overload. In order to solve such an overload problem, if the discharge pressure inside the intermediate pressure chamber is excessive, refrigerant should be discharged even if it has not yet reached the discharge chamber.

If the intermediate pressure increases to be higher than the discharge pressure, the valve body 124 c may move upward to open the bypass hole 149. As the bypass hole 149 is opened, the refrigerant disposed in the intermediate pressure chamber may be discharged into the groove portion 161, and may then move to the discharge space via the discharge path. With such a configuration, pressure of the intermediate pressure chamber may be prevented from excessively increasing.

An operating condition of a system to which a compressor, for example, a scroll compressor, is to be applied may be predetermined. Accordingly, a range of the suction pressure and the discharge pressure of the compressor may be predicted. Based on the predicted range, a position or positions where the intermediate pressure chamber has an excessive pressure may be determined, and overload may be solved by forming bypass holes at those position(s).

In the conventional art, if optimum positions of the bypass holes correspond to an outside of a hub member, the bypass holes cannot be formed at the necessary positions. However, with this embodiment, as the back pressure chamber assembly may be separated from the fixed plate, the bypass holes may be formed at any position on the plate portion of the second scroll. Further, as the bypass valve may be installed, overload may be effectively solved.

The shape of the bypass valve is not limited to the illustrated example.

FIG. 11 is a perspective view of a bypass valve according to an embodiment. In FIG. 11, the bypass valve has a structure in which the valve bodies 124 c may be connected to an edge portion 124 d. More specifically, the valve supporting portions 124 a may be coupled to the plate portion 143 of the second scroll 140, for example, by bolts 106, and may be connected to each other by the edge portion 124 d. The two connection portions 124 b may be connected to a portion of the valve supporting portions 124 a, and the valve bodies 124 c may be formed at ends of the connection portions 124 b.

According to this embodiment, the bypass valve may be fixed by bolts used to connect the second scroll and the back pressure plate to each other, without using an additional coupling device. Accordingly, this may simplify the assembly processes.

FIG. 12 is a cross-sectional view showing a bypass valve according to another embodiment. In FIG. 12, a valve installation hole 152 a may be formed in the groove portion 161, and a bypass valve 220 may be installed in the valve installation hole 152 a. The bypass valve 220 may include a valve body 224 to open and close the bypass hole 149 and a stem 222 formed on a rear surface of the valve body 224. The stem 222 may be installed so as to be movable up and down in the valve installation hole 152 a. A coil spring 226 to press the valve body 224 downward when an external force is not applied to the valve body 224 may be installed on an outer circumferential part of the stem 222.

According to this embodiment, if the pressure inside the intermediate pressure chamber becomes higher than the discharge pressure, the bypass valve 220 may apply a force greater than an elastic force of the coil spring 226 to the coil spring 226. As a result, the bypass valve 220 may move upward. Accordingly, the bypass hole may open, and refrigerant inside the intermediate pressure chamber may be discharged to the discharge space.

According to another embodiment, the coil spring 226 may not be provided. However, even if the coil spring 226 is not provided, the pressure of the discharge space may be applied to an upper surface of the valve body 224. Accordingly, in a case in which the pressure of the intermediate pressure chamber is lower than the pressure of the discharge space, the valve body 224 may cover the bypass hole. If the coil spring 226 is provided, the open valve body may move downward more rapidly, thus enhancing a response of the valve.

FIG. 13 is a perspective view showing a bypass valve according to yet another embodiment. In FIG. 13, a plate portion 243 including a discharge opening 245 at a central portion thereof may be formed on an upper surface of a second scroll 240, and a suction opening 244 may be formed on a side surface of the second scroll 240. Bolt coupling holes 248 may be disposed near an edge of the plate portion 243, and a central portion of the plate portion 243 may be concaved to form a concaved portion 243 a.

A gasket 244 may be provided at a periphery of the discharge opening 245. The gasket 244 may serve to prevent leakage of a refrigerant from a space between the plate portion 243 and the back pressure plate 150. A pair of protrusions 244 a may be formed on an inner circumference portion of the gasket 244. The protrusions 244 a may be coupled to pins 242 installed above the plate portion 243, thereby guiding the gasket 244 to be positioned at a precise position.

The bypass valve may be installed in the gasket 244, and may include valve supporting portions 224 a to insert the pins 242 thereinto, and a connection portion 224 b that extends between the valve supporting portions 224 a. The connection portion 224 b may have an approximate circular shape, and the valve body 224 c may be formed on the connection portion 224 b to open and close the bypass holes.

According to this embodiment, if the back pressure plate and the second scroll are coupled to each other through fitting the bypass valve into the pins, the bypass valve may be coupled to the back pressure plate or the second scroll. This may facilitate the assembly process of the scroll compressor.

Embodiments disclosed herein provide a scroll compressor and a method thereof.

Embodiments disclosed herein a scroll compressor that may comprise a casing; a discharge cover fastened to the casing from within, the discharge cover dividing an inner space of the casing into a suction space and a discharge space; a main frame fastened to the casing from within, the main frame formed spaced apart from the discharge cover; a first or orbital scroll supported by the main frame, the orbital scroll configured to perform an orbital motion with respect to a rotational shaft of the orbital scroll in operation; a second or fixed scroll forming a suction chamber, an intermediate pressure chamber, and a discharge chamber together with the orbital scroll, the fixed scroll formed to be movable with respect to the orbital scroll and comprising a bypass hole that communicates with the intermediate pressure chamber; a back pressure chamber assembly coupled to an upper part of the fixed scroll with a fastening means or fastener, the back pressure chamber assembly being configured to press the fixed scroll toward the orbital scroll by receiving part of an operation fluid from the intermediate pressure chamber, and the back pressure chamber assembly having a discharge path that communicates the discharge chamber and the discharge space with each other; and a bypass valve that opens and closes the bypass hole, where a bypass path by which the bypass hole and the discharge path communicate with each other is formed between the back pressure chamber assembly and the fixed scroll.

Embodiments disclosed herein provide a scroll compressor that may include a casing; a discharge cover fixed to inside of the casing, and dividing the inside of the casing into a suction space and a discharge space; a main frame spaced from the discharge cover; a first or orbital scroll which performs an orbital motion in a supported state on the main frame; a second or fixed scroll installed to be movable up and down with respect to the orbital scroll, forming a suction chamber, an intermediate pressure chamber, and a discharge chamber together with the orbital scroll, and having one or more bypass holes that communicate with the intermediate pressure chamber; a back pressure chamber assembly coupled to an upper part of the fixed scroll to restrict an upward motion of the fixed scroll, configured to press the fixed scroll toward the orbital scroll by introducing (e.g., accommodating, receiving, etc.) part of an operation fluid inside the intermediate pressure chamber, and having a discharge path to communicate the discharge chamber and the discharge space with each other; and a bypass valve to open and close the bypass hole. A bypass path to communicate the bypass hole and the discharge path with each other may be formed between the back pressure chamber assembly and the fixed scroll.

The fixed scroll may be divided into a fixed wrap part and a back pressure chamber part, and a bypass valve and a bypass path may be disposed therebetween before the fixed wrap part and the back pressure chamber part are fastened using a fastening device. This may facilitate installation of the bypass valve, and may allow the bypass hole to be formed at an arbitrary position.

The suction chamber, the intermediate pressure chamber, and the discharge chamber may be some of a plurality of compression chambers formed by the orbital scroll and the fixed scroll. More specifically, the suction chamber may refer to a compression chamber to which a refrigerant has been sucked to start a compression operation. The discharge chamber, which may communicate with a discharge opening, may refer to a compression chamber where a discharge has just begun or is in the process. The intermediate pressure chamber, which may be disposed between the suction chamber and the discharge chamber, may refer to a compression chamber where a compression operation is being processed or performed.

The bypass valve may be configured to be opened and closed by a pressure difference between the intermediate pressure chamber and the discharge space. The pressure of the discharge space may mean an average pressure inside the discharge space, not a pressure of a refrigerant discharged through the fixed scroll.

An open degree restricting means or restrictor that restricts an open degree of the bypass valve may be provided. The open degree restricting means may be formed on a lower surface of the back pressure chamber assembly, and may be provided with an additional retainer. The retainer may be formed to have a shape to optimize an open shape of the bypass valve. The retainer may be additionally provided. Alternatively, a lower surface of the back pressure chamber assembly may be implemented as the retainer.

The bypass path may be defined by a groove portion concaved from a lower surface of the back pressure chamber assembly and an upper surface of the fixed scroll. Further, the bypass path may be defined by a groove portion concaved from an upper surface of the fixed scroll and a lower surface of the back pressure chamber assembly. The bypass valve may be configured to open and close the bypass hole while moving in the groove portion up and down. An amount of the up-and-down motion of the bypass valve may be restricted by an inner surface of the groove portion.

The bypass valve may include a valve body configured to cover the bypass hole and a valve supporting portion or support configured to fix the valve body between the fixed scroll and the back pressure chamber assembly. A single valve supporting portion may be provided with a plurality of valve bodies. For example, the valve supporting portion may be formed to enclose the discharge opening, and the valve body may extend inward from the valve supporting portion in a radial direction. As another example, the valve supporting portion may extend in a ‘V’ shape.

The valve supporting portion may be fixed by a coupling member that couples the back pressure assembly and the fixed scroll to each other or by an additional coupling member. In this case, the valve supporting portion may be fixed to the fixed scroll by, for example, rivets.

A sealing means or seal to enclose the discharge path may be provided between contact surfaces of the back pressure chamber assembly and the fixed scroll.

The back pressure chamber assembly may include a back pressure plate fixed to the fixed scroll below the discharge cover, and provided with a space portion or space an upper part of which is open, the space portion communicating with the intermediate pressure chamber; and a floating plate movably coupled to the back pressure plate so as to seal the space portion, and forming a back pressure chamber.

The back pressure plate may include a supporting plate, which may have a ring shape and may contact an upper surface of the fixed scroll, a first ring-shaped wall formed to enclose an inner space portion of the supporting plate, and a second ring-shaped wall disposed on or at an outer circumferential part of the first ring-shaped wall. A plurality of bolt coupling holes may be formed at or in the supporting plate, and the fixed scroll and the back pressure plate may be coupled to each other by, for exmaple, bolts which pass through the bolt coupling holes.

The floating plate may have a ring shape. The floating plate and the back pressure plate may be coupled to each other such that an outer circumferential surface of the first ring-shaped wall contacts an inner circumferential surface of the floating plate and an inner circumferential surface of the second ring-shaped wall contacts an outer circumferential surface of the floating plate. The second ring-shaped wall may be positioned on an outer circumferential surface of the supporting plate.

A diameter of the bypass hole may be formed to be smaller than a thickness of a wrap of the fixed scroll.

Embodiments disclosed herein further provide a scroll compressor that may include a casing divided into a suction space and a discharge space; a first or orbital scroll configured to perform an orbital motion in operation; a second or fixed scroll which forms a suction chamber, an intermediate pressure chamber, and a discharge chamber together with the orbital scroll; a bypass hole and a bypass valve configured to discharge an operation fluid to outside of the fixed scroll when pressure of the intermediate pressure chamber is higher than a discharge pressure; a discharge path that communicates with the discharge space, and a bypass path forming member configured to introduce the discharged operation fluid inside the intermediate pressure chamber to the discharge path. The discharged operation fluid inside the intermediate pressure chamber may flow between facing surfaces of the fixed scroll and the bypass path forming member, to reach the discharge path.

Embodiments disclosed herein may have at least the following advantages.

First, the fixed scroll may be divided into a fixed wrap part and a back pressure chamber part, and the bypass valve and the bypass path may be disposed therebetween, before the fixed wrap part and the back pressure chamber part are fastened using a fastening device. This may facilitate installation of the bypass valve.

Further, a position of the bypass hole may be arbitrarily set, thereby minimizing occurrence of overload applied to the scroll compressor due to change in an operating condition. Further, even if the scroll compressor is overloaded at an early stage of its operation, the overload may be rapidly removed using the bypass holes and associated components.

Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art. 

1. A scroll compressor, comprising: a casing; a discharge cover, the discharge cover dividing an inner space of the casing into a suction space and a discharge space; a main frame, the main frame being spaced apart from the discharge cover; a first scroll supported by the main frame, the first scroll performing an orbital motion with respect to a rotational shaft thereof in operation; a second scroll that forms a suction chamber, an intermediate pressure chamber, and a discharge chamber together with the first scroll, the second scroll being movable with respect to the first scroll and comprising a bypass hole that communicates with the intermediate pressure chamber; a back pressure chamber assembly coupled to the second scroll, the back pressure chamber assembly comprising a back pressure plate and a floating plate and being configured to press the second scroll toward the first scroll, the back pressure chamber assembly further having a discharge path by which the discharge chamber and the discharge space with communicate with each other; and a bypass valve that opens and closes the bypass hole, wherein a bypass path by which the bypass hole and the discharge path communicate with each other is formed between facing surfaces of the back pressure chamber assembly and the second scroll.
 2. The scroll compressor of claim 1, wherein the back pressure plate includes a groove formed therein and the floating plate is movably disposed in the groove.
 3. The scroll compressor of claim 2, wherein a lower surface of the back pressure plate faces an upper surface of the second scroll.
 4. The scroll compressor of claim 3, wherein the bypass path is formed between the lower surface of the back pressure plate and the upper surface of the second scroll and extends in a lateral direction.
 5. The scroll compressor of claim 1, wherein the bypass path includes a groove formed in one of the lower surface of the back pressure plate or the upper surface of the second scroll.
 6. The scroll compressor of claim 1, wherein the bypass valve is opened and closed by a pressure difference between the intermediate pressure chamber and the discharge space.
 7. The scroll compressor of claim 1, further comprising a restrictor that restricts an open degree of the bypass valve.
 8. The scroll compressor of claim 7, wherein the restrictor is formed on a lower surface of the back pressure chamber assembly.
 9. The scroll compressor of claim 7, wherein the restrictor comprises a retainer disposed on a lower surface of the back pressure chamber assembly.
 10. The scroll compressor of claim 1, wherein the bypass path is defined by a groove concaved from a lower surface of the back pressure chamber assembly, and an upper surface of the second scroll, and wherein the bypass valve is configured to open and close the bypass hole via a movement within the groove.
 11. The scroll compressor of claim 10, wherein the movement of the bypass valve is restricted by an inner surface of the groove.
 12. The scroll compressor of claim 1, wherein the bypass path is defined by a groove concaved from an upper surface of the second scroll and a lower surface of the back pressure chamber assembly, and wherein the bypass valve is configured to open and close the bypass hole via a movement within the groove.
 13. The scroll compressor of claim 12, wherein the movement of the bypass valve is restricted by an inner surface of the groove.
 14. The scroll compressor of claim 1, wherein the bypass valve comprises: a valve body configured to cover the bypass hole; and a valve support configured to fix the valve body between the second scroll and the back pressure chamber assembly.
 15. The scroll compressor of claim 14, wherein the valve body comprises a plurality of valve bodies.
 16. The scroll compressor of claim 15, wherein the valve support encloses the discharge opening, and the plurality of valve bodies extend inwardly from the valve support in a radial direction.
 17. The scroll compressor of claim 15, wherein the valve support extends in a ‘V’ shape.
 18. The scroll compressor of claim 15, wherein the valve support is fixed by a coupling member that couples the back pressure assembly and the second scroll to each other.
 19. The scroll compressor of claim 15, wherein the valve support is fixed to the second scroll by at least one rivet.
 20. The scroll compressor of claim 1, further comprising a seal that encloses the discharge path disposed between contact surfaces of the back pressure chamber assembly and the second scroll.
 21. The scroll compressor of claim 1, wherein the back pressure chamber assembly comprises: a back pressure plate fastened to the second scroll below the discharge cover, the back pressure plate comprising a cavity with which the intermediate pressure chamber communicates; and a floating plate movably coupled to the back pressure plate so as to seal an upper portion of the cavity.
 22. The scroll compressor of claim 21, wherein the back pressure plate comprises: a supporting plate having a ring shape that contacts an upper surface of the second scroll; a first ring-shaped wall formed to enclose an inner space of the supporting plate; and a second ring-shaped wall disposed at an outer circumference of the first ring-shaped wall.
 23. The scroll compressor of claim 22, further comprising a plurality of bolt coupling holes formed on the supporting plate, wherein the second scroll and the back pressure plate are fastened by a corresponding number of bolts, which pass through the plurality of bolt coupling holes.
 24. The scroll compressor of claim 22, wherein the floating plate is ring-shaped, and wherein the floating plate and the back pressure plate are coupled such that an outer circumferential surface of the first ring-shaped wall contacts an inner circumferential surface of the floating plate and an inner circumferential surface of the second ring-shaped wall contacts an outer circumferential surface of the floating plate.
 25. The scroll compressor of claim 22, wherein the second ring-shaped wall is positioned at an outer circumferential surface of the supporting plate.
 26. The scroll compressor of claim 1, wherein a diameter of the bypass hole is formed to be smaller than a thickness of a wrap of the second scroll.
 27. A scroll compressor, comprising: a casing comprising a suction space and a discharge space; a first scroll that forms a suction chamber, an intermediate pressure chamber, and a discharge chamber together with a second scroll; a bypass hole and a bypass valve configured to discharge an operation fluid outside of the second scroll when pressure of the intermediate pressure chamber is higher than a discharge pressure; a discharge path that communicates with the discharge space; and a back pressure plate configured to introduce the discharged operation fluid to the discharge path, wherein the discharged operation fluid flows between facing surfaces of the second scroll and the back pressure plate, to thus reach the discharge path.
 28. The scroll compressor of claim 27, wherein the back pressure plate includes a groove formed therein and the floating plate is movably disposed in the groove.
 29. The scroll compressor of claim 28, wherein a lower surface of the back pressure plate faces an upper surface of the second scroll.
 30. The scroll compressor of claim 29, wherein a bypass path is formed between the lower surface of the back pressure plate and the upper surface of the second scroll and extends in a lateral direction.
 31. The scroll compressor of claim 27, wherein the discharged operation fluid flows along a groove formed in one of a lower surface of the back pressure plate or an upper surface of the second scroll, to thus reach the discharge path
 32. The scroll compressor of claim 27, further comprising a restrictor that restricts an open degree of the bypass valve.
 33. The scroll compressor of claim 32, wherein the restrictor is formed on a lower surface of the back pressure plate.
 34. The scroll compressor of claim 33, wherein the restrictor comprises a retainer disposed on a lower surface of the back pressure plate.
 35. The scroll compressor of claim 27, wherein a bypass path is defined by a groove concaved from a lower surface of the back pressure plate, and an upper surface of the second scroll, and wherein the bypass valve is configured to open and close the bypass hole via a movement within the groove.
 36. The scroll compressor of claim 35, wherein the movement of the bypass valve is restricted by an inner surface of the groove.
 37. The scroll compressor of claim 27, wherein a bypass path is defined by a groove concaved from an upper surface of the second scroll and a lower surface of the back pressure plate, and wherein the bypass valve is configured to open and close the bypass hole via a movement within the groove.
 38. The scroll compressor of claim 37, wherein the movement of the bypass valve is restricted by an inner surface of the groove.
 39. The scroll compressor of claim 27, wherein the bypass valve comprises: a valve body configured to cover the bypass hole; and a valve support configured to fix the valve body between the second scroll and the back pressure plate.
 40. The scroll compressor of claim 39, wherein the valve body comprises a plurality of valve bodies.
 41. The scroll compressor of claim 40, wherein the valve support encloses the discharge opening, and the plurality of valve bodies extend inwardly from the valve support in a radial direction.
 42. The scroll compressor of claim 40, wherein the valve support extends in a ‘V’ shape.
 43. The scroll compressor of claim 40, wherein the valve support is fixed by a coupling member that couples the back pressure plate and the second scroll to each other.
 44. The scroll compressor of claim 40, wherein the valve support is fixed to the second scroll by at least one rivet.
 45. The scroll compressor of claim 27, further comprising a seal that encloses the discharge path disposed between contact surfaces of the back pressure plate and the second scroll.
 46. The scroll compressor of claim 27, wherein the back pressure plate comprises: a supporting plate having a ring shape that contacts an upper surface of the second scroll; a first ring-shaped wall formed to enclose an inner space of the supporting plate; and a second ring-shaped wall disposed at an outer circumference of the first ring-shaped wall.
 47. The scroll compressor of claim 46, further comprising a plurality of bolt coupling holes formed on the supporting plate, wherein the second scroll and the back pressure plate are fastened by a corresponding number of bolts, which pass through the plurality of bolt coupling holes.
 48. The scroll compressor of claim 46, further comprising a ring-shaped floating plate, wherein the floating plate and the back pressure plate are coupled such that an outer circumferential surface of the first ring-shaped wall contacts an inner circumferential surface of the floating plate and an inner circumferential surface of the second ring-shaped wall contacts an outer circumferential surface of the floating plate.
 49. The scroll compressor of claim 46, wherein the second ring-shaped wall is positioned at an outer circumferential surface of the supporting plate.
 50. The scroll compressor of claim 27, wherein a diameter of the bypass hole is formed to be smaller than a thickness of a wrap of the second scroll.
 51. A scroll compressor, comprising: a casing; a discharge cover, the discharge cover dividing an inner space of the casing into a suction space and a discharge space; a main frame, the main frame being spaced apart from the discharge cover; a first scroll supported by the main frame, the first scroll performing an orbital motion with respect to a rotational shaft thereof in operation; a second scroll that forms a suction chamber, an intermediate pressure chamber, and a discharge chamber together with the first scroll, the second scroll being movable with respect to the first scroll and comprising a bypass hole that communicates with the intermediate pressure chamber; a back pressure chamber assembly coupled to the second scroll, the back pressure chamber assembly comprising a back pressure plate and a floating plate and being configured to press the second scroll toward the first scroll, the back pressure chamber assembly further having a discharge path by which the discharge chamber and the discharge space with communicate with each other; and a bypass valve that opens and closes the bypass hole, wherein the back pressure plate comprises a back pressure cavity formed by inner and outer circumferential walls, and wherein the bypass hole is formed in the second scroll at a position outwardly spaced from the inner circumferential wall in a radial direction.
 52. The scroll compressor of claim 51, wherein a lower surface of the back pressure plate faces an upper surface of the second scroll.
 53. The scroll compressor of claim 52, wherein a bypass path is formed between the lower surface of the back pressure plate and the upper surface of the second scroll and extends in a lateral direction.
 54. The scroll compressor of claim 53, wherein the bypass path includes a groove formed in one of the lower surface of the back pressure plate or the upper surface of the second scroll.
 55. The scroll compressor of claim 51, wherein the bypass valve is opened and closed by a pressure difference between the intermediate pressure chamber and the discharge space.
 56. The scroll compressor of claim 51, further comprising a restrictor that restricts an open degree of the bypass valve.
 57. The scroll compressor of claim 56, wherein the restrictor is formed on a lower surface of the back pressure chamber assembly.
 58. The scroll compressor of claim 56, wherein the restrictor comprises a retainer disposed on a lower surface of the back pressure chamber assembly.
 59. The scroll compressor of claim 51, wherein a bypass path is defined by a groove concaved from a lower surface of the back pressure plate, and an upper surface of the second scroll, and wherein the bypass valve is configured to open and close the bypass hole via a movement within the groove.
 60. The scroll compressor of claim 59, wherein the movement of the bypass valve is restricted by an inner surface of the groove.
 61. The scroll compressor of claim 51, wherein a bypass path is defined by a groove concaved from an upper surface of the second scroll and a lower surface of the back pressure plate, and wherein the bypass valve is configured to open and close the bypass hole via a movement within the groove.
 62. The scroll compressor of claim 61, wherein the movement of the bypass valve is restricted by an inner surface of the groove.
 63. The scroll compressor of claim 51, wherein the bypass valve comprises: a valve body configured to cover the bypass hole; and a valve support configured to fix the valve body between the second scroll and the back pressure plate.
 64. The scroll compressor of claim 63, wherein the valve body comprises a plurality of valve bodies.
 65. The scroll compressor of claim 64, wherein the valve support encloses the discharge opening, and the plurality of valve bodies extend inwardly from the valve support in a radial direction.
 66. The scroll compressor of claim 64, wherein the valve support extends in a ‘V’ shape.
 67. The scroll compressor of claim 64, wherein the valve support is fixed by a coupling member that couples the back pressure plate and the second scroll to each other.
 68. The scroll compressor of claim 64, wherein the valve support is fixed to the second scroll by at least one rivet.
 69. The scroll compressor of claim 51, further comprising a seal that encloses the discharge path disposed between contact surfaces of the back pressure plate and the second scroll.
 70. The scroll compressor of claim 51, wherein the back pressure plate comprises: a supporting plate having a ring shape that contacts an upper surface of the second scroll; a first ring-shaped wall formed to enclose an inner space of the supporting plate; and a second ring-shaped wall disposed at an outer circumference of the first ring-shaped wall.
 71. The scroll compressor of claim 70, further comprising a plurality of bolt coupling holes formed on the supporting plate, wherein the second scroll and the back pressure plate are fastened by a corresponding number of bolts, which pass through the plurality of bolt coupling holes.
 72. The scroll compressor of claim 70, wherein the floating plate is ring-shaped, and wherein the floating plate and the back pressure plate are coupled such that an outer circumferential surface of the first ring-shaped wall contacts an inner circumferential surface of the floating plate and an inner circumferential surface of the second ring-shaped wall contacts an outer circumferential surface of the floating plate.
 73. The scroll compressor of claim 70, wherein the second ring-shaped wall is positioned at an outer circumferential surface of the supporting plate.
 74. The scroll compressor of claim 51, wherein a diameter of the bypass hole is formed to be smaller than a thickness of a wrap of the second scroll. 